Higher rates of obesity, sedentary lifestyle, and coronary heart disease are observed in rural than in non-rural areas of the U.S., yet the treatment of obesity in the rural population has received little attention. Efficacy trials, conducted in academic health centers, show that lifestyle interventions can produce sufficient weight reductions to improve health, but very few trials have been carried out in medically underserved community settings. Moreover, the high intensity of treatments used in efficacy studies represents a barrier to dissemination into rural settings. The existing infrastructure of the USDA Cooperative Extension Service, with over 2900 offices nationwide, may serve as a valuable resource for bringing lifestyle interventions to rural areas. Preliminary data from our rural obesity research program show promising findings for lifestyle interventions delivered through Extension offices. The next logical step in this line of research is to determine the minimum intensity of treatment required to produce clinically meaningful, long-term weight reductions. We propose to conduct a single-blind, multi-site, randomized controlled trial in obese adults (N=542) to evaluate the effects of LOW, MODERATE, and HIGH doses of lifestyle treatment on two-year changes in body weight, compared to an education CONTROL condition. The LOW intensity condition reflects the dose of group treatment commonly used in community settings, whereas the HIGH dose corresponds to the intensity level employed in efficacy trials. The MODERATE intensity intervention represents a treatment dose that our preliminary data suggest may provide benefits comparable to the HIGH intensity intervention. Our principal hypothesis is that both the MODERATE and HIGH interventions will produce greater weight reductions at two years than either the LOW or CONTROL conditions. We will also evaluate the proportion of participants in each condition, who achieve clinically significant weight losses, and we will examine changes in metabolic risk factors, dietary intake, physical activity, and quality of life. We will calculate the cost-effectiveness of the interventions, and we will investigate potential mediators of long-term change.